Inhibition of bacterial DNA replication by zinc mobilization during nitrosative stress

Schapiro, Jeffrey M.; Libby, Stephen J.; Fang, Ferric C.

doi:10.1073/pnas.1033133100

Cited by 109 publications

(95 citation statements)

References 52 publications

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“…Thus, when used at a high concentration (35 nmol/ml/min vs. Ϸ0.5 nmol/ml/min in our experiments), NO may act as an inducer of the SOS response in E. coli (31); in these conditions, the recA deletion leads to a high sensitivity to NO (31), demonstrating that the SOS response is induced and essential to fight the deleterious effects of NO. Nevertheless, ''physiological'' amounts of NO do not stimulate the SOS response in Salmonella enterica because RecA is not essential to prevent NO-dependent bacterial DNA fragmentation (32). Moreover, several transcriptomic analysis of E. coli demonstrated that expression of the genes of the SOS response was not enhanced following exposure to NO (18)(19)(20)(21).…”

Section: Discussionmentioning

confidence: 99%

Nitric oxide inhibits Shiga-toxin synthesis by enterohemorrhagic Escherichia coli

Vareille¹,

Sablet²,

Hindré³

et al. 2007

Proc. Natl. Acad. Sci. U.S.A.

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Shiga-toxin (Stx) is the cardinal virulence factor of enterohemorrhagic Escherichia coli (EHEC). The genes encoding Stx are carried by a lambdoid phage integrated in the bacterial genome and are fully expressed after a bacterial SOS response induced by DNAdamaging agents. Because nitric oxide (NO) is an essential mediator of the innate immune response of infected colonic mucosa, we aimed to determine its role in Stx production by EHEC. Here we demonstrate that chemical or cellular sources of NO inhibit spontaneous and mitomycin C-induced stx mRNA expression and Stx synthesis, without altering EHEC viability. The synthesis of stx phage is also reduced by NO. This inhibitory effect apparently occurs through the NO-mediated sensitization of EHEC because mutation of the NO sensor nitrite-sensitive repressor results in loss of NO inhibiting activity on stx expression. Thus our findings identify NO as an inhibitor of stx expressing-phage propagation and Stx release and thus as a potential protective factor limiting the development of hemolytic syndromes.bacterial infection ͉ mucosal immunology E nterohemorrhagic Escherichia coli (EHEC) are pathogens carried by healthy rearing animals. After infection through the ingestion of contaminated food, EHEC colonize the large intestine and cause gastrointestinal diseases ranging from uncomplicated diarrhea to hemorrhagic colitis. Life-threatening complications, such as hemolytic-uremic syndrome (HUS), develop in Ϸ5-10% of EHEC-infected patients. HUS is defined by a triad of microangiopathic hemolytic anemia, thrombocytopenia, and acute renal failure, which can yield to a chronic renal failure and even death (1-3). O157:H7 is the main EHEC serotype implicated in HUS in Europe and North America (3). The few recent large outbreaks (4, 5) underline that prevention of primary infection in human remains an elusive goal. Therefore, understanding host-EHEC interactions remains a critical issue in fighting bacterial infection and HUS development.The main EHEC virulence factor associated with severe human diseases is the Shiga toxin (Stx). Both Stx1 and Stx2 are heteropolymers constituted by a catalytic A subunit and five B subunits implicated in the binding to the receptor glycolipid globotriaosylceramide-3 of endothelial cells. Internalized Stx alters ribosomal function and induces the death of vascular cells (1, 3). Stx1 and Stx2 are encoded by two type lysogenic phages integrated in the bacterial genome (6). In a lysogen, the expression of the phage operons is controlled by the protein CI. As a result of EHEC exposure to DNA-damaging agents such as mitomycin C (7) or H 2 O 2 (8), RecA, which is part of the so-called SOS response, is activated by single-strand DNA and promotes the autocleavage of CI (9). Then, a regulatory cascade yields to the respective expression of the genes encoding the antiterminators N and Q, Stx, and proteins of phage morphogenesis and lysis (9-13). Bacteria are lysed and release Stx and free phage particles in the medium.An important hallmark of EHEC pathoge...

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Section: Discussionmentioning

confidence: 99%

Nitric oxide inhibits Shiga-toxin synthesis by enterohemorrhagic Escherichia coli

Vareille¹,

Sablet²,

Hindré³

et al. 2007

Proc. Natl. Acad. Sci. U.S.A.

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“…In the presence of nitric oxide, S. enterica requires RecBC but not RecA for viability and undergoes RuvABC-dependent chromosome breakage in the recB background. These observations led to the proposal that upon infection, the inhibition of S. enterica replication by macrophageproduced nitric oxide causes replication fork reversal, which is lethal for the S. enterica recB mutant and thus accounts for its decreased virulence (63). Despite a high conservation of structure and function of replication and recombination proteins, replication arrests in eukaryotes will clearly have consequences different from those in prokaryotes.…”

Section: Resultsmentioning

confidence: 99%

“…Another example of replication fork reversal in bacteria was observed in Salmonella enterica serovar Typhimurium, a close relative of E. coli. A recB derivative of S. enterica is highly attenuated for virulence (63). The nitric oxide produced by macrophages when they ingest S. enterica causes bacterial replication inhibition.…”

Section: Resultsmentioning

confidence: 99%

Multiple pathways process stalled replication forks

Michel

Grompone

Flores

et al. 2004

Proc. Natl. Acad. Sci. U.S.A.

309

330

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Impairment of replication fork progression is a serious threat to living organisms and a potential source of genome instability. Studies in prokaryotes have provided evidence that inactivated replication forks can restart by the reassembly of the replication machinery. Several strategies for the processing of inactivated replication forks before replisome reassembly have been described. Most of these require the action of recombination proteins, with different proteins being implicated, depending on the cause of fork arrest. The action of recombination proteins at blocked forks is not necessarily accompanied by a strand-exchange reaction and may prevent rather than repair fork breakage. These various restart pathways may reflect different structures at stalled forks. We review here the different strategies of fork processing elicited by different kinds of replication impairments in prokaryotes and the variety of roles played by recombination proteins in these processes.W ork from several laboratories has established that in bacteria, a recombination event can lead to the establishment of a unidirectional replication fork (reviewed in refs. 1-3). These observations extend the concept of a direct recombination-replication connection, originally proposed Ϸ30 years ago from studies of bacteriophage T4 and replication. Furthermore, the existence of recombination-dependent replication in yeast suggests that this connection may be a widely distributed phenomenon (4, 5).Considering the tight control of replication initiation at chromosomal origins, the assembly of a complete replisome at recombination intermediates, independently of time and place, is paradoxical. One of the raisons d'être of this potentially dangerous process was revealed by the finding that recombination intermediates form at inactivated replication forks and are used for replication restart. However, studies of the replicationrecombination connection in Escherichia coli have indicated that recombination proteins do not necessarily catalyze strand exchange at blocked forks and rather act in a variety of reactions that depend on the origin of the arrest. We review here the diversity of fates of inactivated replication forks in bacteria, as well as our present knowledge of the roles played by recombination proteins during replication restart. DNA Double-Strand End Repair in BacteriaAlmost 30 years ago, Higgins et al. (6) proposed that blocked replication forks could be isomerized into a four-way Holliday junction (HJ) with a DNA double-strand end, which could permit DNA repair and then continuation of replication (Fig. 1, step A). The test of the model, performed by treatment of mammalian cells with a DNA-damaging agent, was inconclusive (7). However, more recent studies in E. coli suggest that such replication fork reversal plays a crucial role in replication restart in bacteria (8,9).A key aspect of the replication fork reversal model is that it generates a DNA double-strand end at blocked forks without chromosome breakage. In E. coli, the enzyme th...

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“…Microbial targets of RNI include thiols, metal centers, lipids and DNA. NO itself is considered to be bacteriostatic and NO-related toxicity includes inhibition of respiration [3] and reduced cell division by disrupting DNA replication [4]. In approximately 80 % of the community-acquired urinary tract infections (UTIs) the cause of the infection is a uropathogenic Escherichia coli (UPEC) strain.…”

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confidence: 99%

Role of flavohemoglobin in combating nitrosative stress in uropathogenic Escherichia coli – Implications for urinary tract infection

Svensson

Poljakovic

Säve

et al. 2010

Microbial Pathogenesis

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Role of flavohemoglobin in combating nitrosative stress in uropathogenic Escherichia coliimplications for urinary tract infection. During the course of urinary tract infection (UTI) nitric oxide (NO) is generated as part of host response. The aim of this study was to investigate the significance of the NO-detoxifying enzymes flavohemoglobin (Hmp) and flavorubredoxin (Norv) in protection of uropathogenic Escherichia coli (UPEC) against nitrosative stress. Hmp (J96∆hmp) and norV (J96∆norV) knockout mutants of UPEC strain J96 were constructed using a single-gene deletion strategy. Bacterial tolerance and expression of hmp and norV in response to the NO-donor DETA/NO was evaluated in Luria broth and urine from healthy volunteers. Bacterial NO consumption and respiratory inhibition were assessed when exposed to NO. Expression of hmp and norV from E. coli originating from patients with UTI was evaluated using real-time PCR. The colonizing ability of J96 wild-type (wt) compared to an hmp-deficient mutant was assessed using a competition-based mouse UTI model. The viability of J96∆hmp and J96∆norV was significantly reduced compared to the wildtype strain after exposure to DETA/NO. The hmp expression in DETA/NO-exposed cultures was similar in J96wt and J96∆norV, while J96∆hmp showed an increased norV expression compared to J96wt. The NO consumption in J96∆hmp, but not in J96∆norV, was significantly impaired compared to J96wt. An up-regulation of hmp expression was found in E. coli isolated from all UTIpatients while norV expression increased in 50% of the patients. In the mouse UTI model, the hmp-mutant strain was significantly out-competed by the wild-type strain in the bladder and kidney. Hmp and NorV contribute to the protection of UPEC against NOmediated toxicity in vitro. Screening UPEC isolates from UTI patients revealed an increased hmp expression in all patients which confirms that hmp expression occurs in vivo in the infected human urinary tract. The ability to colonize the mouse urinary tract was impaired in the hmp-deficient mutant compared to the wild-type strain. NO-detoxification by Hmp is suggested to be an important characteristic for UPEC in protection against nitrosative stress and may be a virulence-facilitating factor.

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Inhibition of bacterial DNA replication by zinc mobilization during nitrosative stress

Cited by 109 publications

References 52 publications

Nitric oxide inhibits Shiga-toxin synthesis by enterohemorrhagic Escherichia coli

Nitric oxide inhibits Shiga-toxin synthesis by enterohemorrhagic Escherichia coli

Multiple pathways process stalled replication forks

Role of flavohemoglobin in combating nitrosative stress in uropathogenic Escherichia coli – Implications for urinary tract infection

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